Zinc base alloys



Patented Dec. 11, 1945 ZINC BASE ALLQYS Edward S. lBunn, Baltimore, Md, assignor to Revere Copper and Brass incorporated, Home, N. Y., a corporation of Maryland No Drawing. Application November 23, 1043,

Serial No. dlllhi i a claims. (on. as ram My invention, which relates to zinc base alloys and has among its objects the provision of a zinc base alloy of improved characteristics, will be best understood from the following description, the scope of the invention being more particularly pointed out in the appended claims.

The alloys according to the invention contain small amounts of copper, silicon and arsenic within the ranges and proportions hereinafter more particularly pointed out.

Zinc, it will be understood, is a hot and cold workable ductile metal of low tensile strength and toughness. As zinc ages its tensile strength seriously decreases, while its ductility and toughness almost disappear. In commercial applications of zinc it therefore is desirable to increase its tensile strength and toughness while maintaining its ductility and workability, and at the same time prevent its ductility and improved tensile strength and toughness from deleteriously decreasing as the metal ages. Further, it is necessary to secure these results without .making the metal subject as it ages to deleterious intercrystalline corrosion or deleterious dimensional change, which effects are commonly encountered in the attempt to secure such results by adding small amounts of other substances to zinc.

Applicant has found that by adding small amounts of copper, silicon and arsenic to zinc within proper ranges and proportions the tensile gree of toughness coupled with good ductility and high tensile strength will be secured with the improved alloy when throughout the entire range of copper the percentage amount of arsenic present is not greater than the percentage amount of silicon present when the latter is between ap-- proximately 014 and 0.6%. Appreciable results, it has been found, will be secured with as little as 0.05% silicon and 0.1% arsenic, but with more than 0.6% of either of these elements in combination with any amount of the other within the strength and toughness of the zinc may be much increased without seriously decreasing its duetility, and in fact in most instances improving the latter. As the resulting alloy ages a high degree of toughness is maintained, in fact in most instances the toughness markedly increases. At the same time the ductility of the aged alloy is about as good as that of the unaged alloy. Further, the tensile strength of the aged alloy is only slightly inferior to that of the unaged alloy, and in all instances is very much superior to that of zinc. Still further, the alloy is hot and cold workable; being readily hot and cold rolled into sheets, extruded, drawn and forged by ordinary commercial mill processes. And all these results are secured without making the alloy subject to intercrystalline corrosion, or making it unsatisfactory in respect to dimensional change with age.

It has been found that the above results will be secured by additions to zinc of 0.2 to 5% copper, 0.05 to 0.6% silicon, and 0.1 to 0.6% arsenic, provided the sum of the percentage amounts of silicon and arsenic present does not exceed the percentage amount of copper present.

Decidedly best results in respect to a high deranges thereof specified the ductility of the alloy becomes poor and the alloy commonly subject to intercrystalline corrosion and deleterious dimensional change as it ages.

As to the effect of variations in the amount of copper, best results will be secured in respect to a high degree of toughness and ductility with amounts of copper from about 0.8 to 2%, and best results in respect to tensile strength with amounts of copper in excess of 2%, this increase in tensile strength caused by raising the copper content being commonly accompanied by some decrease in the ductility and toughness although the ductilit is still excellent and the toughness still very high. With less than about 0.2% copper no appreciable increase in the tensile strength Of the zinc will be secured, and the alloy will be commonly subject as it ages to a deleterious decrease in tensile strength, toughness and ductility. 0n the other hand, with more than about 5% copper the alloy cannot be readily cold worked by commercial mill processes.

Further, to secure best results in respect to resistance to corrosive media and freedom from intercrystalline corrosion it is desirable to employ in the improved alloy commercial zinc of fairly high purity as, for example, that termed High Grade No. 1 in A.'S. T. M. specification 136-37, which latter grade contains a maximum of 0.07% each of lead and cadmium impurities and a maximum of 0.02% iron impurity, the total of such of these impurities as may be present not exceeding about 0.1%, and is substantially free from all other impurities. With poorer commercial grades of zinc the alloy commonly will have the same mechanical characteristics, but may be somewhat less corrosion resistant in both respects mentioned and have more or less dimensional instability, although ordinarily such impurities as iron, manganese, nickel and cobalt will have no deleterious effect unless present in excessive amounts.

The excellent properties of the improved alloy are exhibited by the following table, in which the steam test mentioned consists in subjecting the alloy to moist steam at 95 C. for days, which Hot rolled, and sub- Percentages As hot rolled lecged to steam Cu 81 As T E C T E C T=tenslle strength in 1,000 pounds per square inch.

E=percent elongation in 2 inches. C=Oharpy impact strength in foot pounds per square inch.

It will be understood that within the scope of 20 the appended claims further constituents may be added for modifying the properties of the improved alloy or for securing additional properties so long as the characteristics imparted to the zinc by the addition of copper, silicon and arsenic are 25 not substantially destroyed.

I claim:

1. Zinc base alloys containing copper, silicon and arsenic within ranges and proportions approximately as follows: copper 0.2 to 5%, silicon 0.05 to 0.6%, arsenic 0.1 to 0.6%, the balance constituting approximately 93.8 to 99.65% of the alloy being substantially zinc, the sum of the percentage amounts of silicon and arsenic present not exceeding the percentage amount of copper present. i

2. Zinc base alloys according to claim 1 in which the percentage amount of arsenic present does not exceed the percentage amount of silicon present when the latter is from 0.4 to 0.6%.

3. Zinc base alloys according to claim 1 having 0.8 to 2% copper, the balance constituting approximately 96.8 to 99.15% of the alloy.

4. Zinc base alloys accordingto claim 1 having 0.8 to 2% copper, and in which the percentage amount of arsenic present does not exceed the percentage amount of silicon present when the latter is from 0.4 to 0.6%, the balance constituting approximately 96.8 to 99.15% of the alloy.

5. Zinc base alloys having, approximately, 2 to 5% copper, 0.05 to 0.6% silicon, and 0.1 to 0.6% arsenic, the balance constituting approximately 93.8 to 97.85% of the alloy being substantially zinc.

6. Zinc base alloys according to claim 5 in which the percentage amount of arsenic present does not exceed the percentage amount of silicon present when the latter is from 0.4 to 0.6%.

EDWARD s. BUNN. 

